svn commit: r347239 - head/sys/dev/random

[Conrad Meyer]

Unfortunately, no real knob for it. I have proposed disabling the warning
in
https://reviews.freebsd.org/D20195 .

Sorry about the noise.

Best,
Conrad

On Wed, May 8, 2019 at 2:08 AM Michael Tuexen <tuexen at freebsd.org> wrote:

> > On 8. May 2019, at 02:45, Conrad Meyer <cem at FreeBSD.org> wrote:
> >
> > Author: cem
> > Date: Wed May  8 00:45:16 2019
> > New Revision: 347239
> > URL: https://svnweb.freebsd.org/changeset/base/347239
> >
> > Log:
> >  random: x86 driver: Prefer RDSEED over RDRAND when available
> I get a lot of
> random_sources_feed: rs_read for hardware device 'Intel Secure Key RNG'
> returned no entropy.
> entries in /var/log/messages now...
>
> Any idea how to turn them off?
>
> Best regards
> Michael
> >
> >  Per
> >
> https://software.intel.com/en-us/blogs/2012/11/17/the-difference-between-rdrand-and-rdseed
> >  , RDRAND is a PRNG seeded from the same source as RDSEED.  The source is
> >  more suitable as PRNG seed material, so prefer it when the RDSEED
> intrinsic
> >  is available (indicated in CPU feature bits).
> >
> >  Reviewed by: delphij, jhb, imp (earlier version)
> >  Approved by: secteam(delphij)
> >  Security:    yes
> >  Sponsored by:        Dell EMC Isilon
> >  Differential Revision:       https://reviews.freebsd.org/D20192
> >
> > Modified:
> >  head/sys/dev/random/ivy.c
> >
> > Modified: head/sys/dev/random/ivy.c
> >
> ==============================================================================
> > --- head/sys/dev/random/ivy.c Wed May  8 00:40:08 2019        (r347238)
> > +++ head/sys/dev/random/ivy.c Wed May  8 00:45:16 2019        (r347239)
> > @@ -44,11 +44,13 @@ __FBSDID("$FreeBSD$");
> >
> > #include <machine/md_var.h>
> > #include <machine/specialreg.h>
> > +#include <x86/ifunc.h>
> >
> > #include <dev/random/randomdev.h>
> >
> > #define       RETRY_COUNT     10
> >
> > +static bool has_rdrand, has_rdseed;
> > static u_int random_ivy_read(void *, u_int);
> >
> > static struct random_source random_ivy = {
> > @@ -57,10 +59,9 @@ static struct random_source random_ivy = {
> >       .rs_read = random_ivy_read
> > };
> >
> > -static inline int
> > -ivy_rng_store(u_long *buf)
> > +static int
> > +x86_rdrand_store(u_long *buf)
> > {
> > -#ifdef __GNUCLIKE_ASM
> >       u_long rndval;
> >       int retry;
> >
> > @@ -75,11 +76,40 @@ ivy_rng_store(u_long *buf)
> >           : "+r" (retry), "=r" (rndval) : : "cc");
> >       *buf = rndval;
> >       return (retry);
> > -#else /* __GNUCLIKE_ASM */
> > -     return (0);
> > -#endif
> > }
> >
> > +static int
> > +x86_rdseed_store(u_long *buf)
> > +{
> > +     u_long rndval;
> > +     int retry;
> > +
> > +     retry = RETRY_COUNT;
> > +     __asm __volatile(
> > +         "1:\n\t"
> > +         "rdseed     %1\n\t" /* read randomness into rndval */
> > +         "jc         2f\n\t" /* CF is set on success, exit retry loop */
> > +         "dec        %0\n\t" /* otherwise, retry-- */
> > +         "jne        1b\n\t" /* and loop if retries are not exhausted */
> > +         "2:"
> > +         : "+r" (retry), "=r" (rndval) : : "cc");
> > +     *buf = rndval;
> > +     return (retry);
> > +}
> > +
> > +DEFINE_IFUNC(static, int, x86_rng_store, (u_long *buf), static)
> > +{
> > +     has_rdrand = (cpu_feature2 & CPUID2_RDRAND);
> > +     has_rdseed = (cpu_stdext_feature & CPUID_STDEXT_RDSEED);
> > +
> > +     if (has_rdseed)
> > +             return (x86_rdseed_store);
> > +     else if (has_rdrand)
> > +             return (x86_rdrand_store);
> > +     else
> > +             return (NULL);
> > +}
> > +
> > /* It is required that buf length is a multiple of sizeof(u_long). */
> > static u_int
> > random_ivy_read(void *buf, u_int c)
> > @@ -90,7 +120,7 @@ random_ivy_read(void *buf, u_int c)
> >       KASSERT(c % sizeof(*b) == 0, ("partial read %d", c));
> >       b = buf;
> >       for (count = c; count > 0; count -= sizeof(*b)) {
> > -             if (ivy_rng_store(&rndval) == 0)
> > +             if (x86_rng_store(&rndval) == 0)
> >                       break;
> >               *b++ = rndval;
> >       }
> > @@ -104,14 +134,14 @@ rdrand_modevent(module_t mod, int type, void
> *unused)
> >
> >       switch (type) {
> >       case MOD_LOAD:
> > -             if (cpu_feature2 & CPUID2_RDRAND) {
> > +             if (has_rdrand || has_rdseed) {
> >                       random_source_register(&random_ivy);
> >                       printf("random: fast provider: \"%s\"\n",
> random_ivy.rs_ident);
> >               }
> >               break;
> >
> >       case MOD_UNLOAD:
> > -             if (cpu_feature2 & CPUID2_RDRAND)
> > +             if (has_rdrand || has_rdseed)
> >                       random_source_deregister(&random_ivy);
> >               break;
> >
> >
>
>